(1) Field of the Invention
The present invention relates to sonar sound sources and more particularly to a surface deployed buoy that generates underwater sonic impulses by releasing acoustic charges at pre-set intervals. The device is autonomous and does not require external control signals or a nearby control signal generating vessel.
(2) Description of the Prior Art
Use of underwater explosive charges to provide sonic impulses is well known in the art. Echo location, sensor testing and signalling are some of the applications requiring underwater deployment of such sonic charges. In echo location the sonic charge is used in the vicinity of hydrophones to provide an impulse for echo location of submerged geologic structures or vessels. In sensor testing applications sonic charges are released at a fixed depth and distance to determine the performance characteristics of underwater sensors. Underwater charges can also be timed to explode in a coded pattern to communicate between a subsurface craft and a hydrophone.
Submarine launched acoustic charge release devices are often deployed for covertly signalling surface craft. The device used in covert signalling must be launched from a torpedo tube and provide coded release of signal charges. The device should not be visible from the surface. In one prior art device exploding bolts are used to separate the charge containing portion of the device from the control portion of the device. Charges are ejected in a coded sequence by explosive bolts in the charge containing portion of the device. A drogue is deployed from the control portion of the device to control the release of charges and prevent the ejection charge from damaging the control portion.
Aircraft deployed acoustic charge release devices are typically used in echo location applications. In this use, the explosion of a charge provides a sound source, and a sonobuoy dropped from the airplane act as pickup devices for echo location of submarines and underwater objects. Aircraft deployed devices are designed to release an underwater charge from a device containing a plurality of charges in response to a radio signal. The aircraft deployed device releases charges arrayed on a streamer to allow detonation when the buoy is signalled.
In test applications, charges are often deployed in the vicinity of an array of submarine acoustic sensors. Acoustic charges must be pressure sensitive to explode at a pre-set depth and the charges must be deployed within a standard distance from the array. The United States Navy has standard acoustic charges, known as signal underwater sound (SUS) charges, available for use in this application. If a surface vessel is used to deploy the charges, after deployment of a charge the vessel must be moved away from the charge deployment site to avoid interference with the acoustic signal because of echo from the hull or engine noise.
Each of the above methods of underwater acoustic charge deployment is deficient when deploying acoustic charges for test purposes. When testing acoustic sensors, charges must be released near the sensor with consistency. Neither aircraft nor submarines can release an acoustic source with sufficient accuracy for test purposes. Existing submarine and aircraft acoustic source devices do not allow for depth sensitive charges. Furthermore, aircraft and submarine deployment is too expensive to be practical for test purposes. Releasing acoustic charges from surface vessels is unavailable because of echo caused by the presence of the vessel and engine noise.